Method of making an aluminum base alloy article



Jan. 10, 1961 s. e. ROBERTS El'AL 2,967,351

METHOD OF MAKING AN ALUMINUM BASE ALLOY ARTICLE Filed Dec. 14, 1956 INVENTORS SIDNEY G. ROBERTS MAURICE C. FETZER JAMES B. HESS United States Patent METHOD OF MAKING AN ALUll/HNUM BASE ALLOY ARTICLE Sidney G. Roberts, Opportunity, and Maurice C. Fetzer and James B. Hess, Spokane, Wash., assignors to Kaiser Aluminum and Chemical Corporation, Oakland, Calif., a corporation of Delaware Filed Dec. 14, 1956, Ser. No. 628,297

16 Claims. (Cl. 29-4205) This invention relates to alloys characterized by superior elevated temperature properties. More particularly this invention relates to aluminum base alloys and to methods for producing aluminum base alloy articles characterized by superior elevated temperature properties, said alloys containing alloying additions in amounts exceeding that heretofore possible in the production of sound and workable cast bodies.

By the term fworkable as used hereinafter is meant that the cast body can be subjected to metal deforming operations such as rolling, forging, and extruding. The design of present and future aircraft and air weapons for operation at high unit stress levels and at speeds where considerable aerodynamic heat occurs has created a critical need for better light weight aircraft structural materials having higher strength, higher modulus of elasticity and greatly improved elevated temperature properties than those heretofore attainable.

It is well recognized that possibilities for obtaining such improved properties with prior art aluminum base alloys are quite limited. This is especially true insofar as elevated temperature properties are concerned.

The high strength aluminum base alloys fabricated under conventional procedures are limited to those alloy systems in which there is an appreciable equilibrium solid solubility of the alloying elements in aluminum. As the alloying elements have appreciable rates of diffusion in aluminum at elevated temperature, the high temperature stability of these alloys is seriously impaired. Consequently, exposure of the conventional precipitation hardened aluminum base alloys to high temperature service results in rapid overaging and attendant decreases in mechanical properties.

The development of alum.num base alloys which would have sufiiciently high elevated temperature properties for present aircraft uses has been hindered by the fact that most alloying additions, which have low diffusion rates at elevated temperatures and consequently could yield stable alloys, form coarse primary crystals of intermediate phases with aluminum or other alloying additions, and cause severe chemical segregation during solidification from the molten state when added in amounts greater than a few atomic percent, or in many cases a few tenths of an atomic percent. These alloying additions upon solidification of the casting tend to concentrate in large coarse intermediate phase particles wh.ch have negligible or very limited solubility in solid aluminum and in this form such alloying additions make a minimum contribution to the mechanical properties of the alloy. Thus the presence .of large amounts of such ice alloying additions generally result in cast bodies which are unsound and difiicult or impossible to process.

Accordingly it is an object of this invention to provide novel aluminum base alloy compositions and methods for producing articles from these compositions which are characterized by superior elevated temperature properties.

It is a further object of this invention to provide methods for producing aluminum base alloy articles containing alloying additions in amounts exceeding that heretofore possible in the production of sound and workable cast bodies.

It is a still further object of this invention to produce aluminum base alloy articles, characterized by superior elevated temperature properties, containing alloying additions of metals in amounts which under conditions of production heretofore known would form coarse primary crystals of intermediate phases with aluminum or other alloying additions and would cause severe chemical segregation during solidification.

It is 'a' still further object of this invention to produce aluminum base alloy articles characterized by superior elevated temperature properties, containing alloying additions of at least one other metal such as chromium, manganese, iron, zirconium, titanium anadium and molybdenum in amounts exceeding that heretofore possible in the production of sound and workable ast bodies. V

These and other objects and advantages of the invention will be apparent from the ensuing detailed description of the invention.

in accordance with this invention, a melt of the desired composition is first heated to a temperature at which it is a homogeneous liquid solution. The liquid solution is then coinminuted at this temperature by'one of several methods whereby the individual particles formed are solidified and cooled at a rate sufficiently rapid to eliminate or substantially eliminate formation of coarse crystals of intermediate phases. 'For example, atomizing or shotting is satisfactory, In the resulting aluminum alloy particle, the undesirable characteristics outlined above as resulting from the presence of relatively large additions of certain alloying elements have been found to have been eliminated or greatly minimized. The solidified particles are then subsequently consolidated by working into larger bodies which are suitable for direct application or subsequent wrought metal fabrication procedures, such as extruding.

The rapid cooling rate of the comminution process greatly extends the amounts of the alloying additions which may be beneficially contained in aluminum alloys. Many compositions may be prepared in accordance with this invention which have received little, if any, consideration in the prior art of aluminum alloy development because it is well known that when such alloy compositions are prepared by conventional casting procedures sound and workable material is not produced.

According to this invention, it has been found that aluminum base alloys containing alloying additions of production of sound'and workable cast bodies can be produced. These alloys are characterized by superior elevated temperature properties. One such alloy con- :sists essentially of, by weight, from 4.5 to 13% copper, 1.5 to 5.0% manganese, 0.2 to 2.0% zirconium and 0.1 :to 1.0% vanadium, balance aluminum and impurities in :normal amounts. Superior elevated temperature properties have also been obtained with binary aluminum base alloys containing one of the following alloying additions in the recited amounts: from 3 to 10% manganese, 1 to 6% zirconium, 3 to 12% iron, 2.5 to molybdenum, l to 6% chromium, 0.5 to 4% titanium, or 0.1 to 2.5% vanadium.

Specific examples illustrating these and other alloys which have been produced by the method of this invention but not constituting a limitation thereto are given in Table I.

TABLE I Chemical composition of aluminum alloy powders in percent by weight Alloy Fe Cu Balance.

The alloys of Table I were prepared by first comminuting a homogeneous liquid solution of a melt having the final desired alloy composition by atomization with an apparatus illustrated with reference to Figure 1.

This apparatus consists of a graphite crucible 1 having a 1" diameter graphite rod 2 afiixed to thelower portion thereof. Graphite rod 2 has a longitudinal tubular passage or hole 3 provided therein in open communication with the interior 4 of graphite crucible 1. Positioned about graphite rod 2 is provided a ring type header 5 having a plurality of gas nozzles 6 connected thereto and in open communication with the hollow interior of header 5. Nozzles 6 are directed downwardly at an angle such that lines drawn through the axes of nozzles 6 intersect at a point below graphite rod 2. A suitable hose or pipe 7 is connected to header 5. Pipe 7 is connected to a source of gas (not shown), for example air, under pressure. Immediately below rod 2 may be provided a container 8 containing a chilling liquid such as water 9.

The molten metal 11 to be atomized is contained in graphite crucible 1 from which it passes through hole 3 in rod 2. By passing a gas such as air under pressure into header 5 jets 13 of such gas will issue from nozzles 6 forming a cone of jets intersecting at a point below hole 3 in rod 2. The molten metal issuing from the bottom of the hole 3 is thus atomized by the cone of air jets whereby the,'resulting particles 12 are rapidly solidified and collected in container 8. While the atomization provides sufiiciently rapid cooling to solidify particles 12 the added cooling provided by liquid 9 prevents the particles from sticking together.

It is to be distinctly understood that the apparatus above described is but one means for comminuting the molten metal and is given by way of example only and it is to be distinctly understood that the invention is not to be limited to the use of such a specific apparatus or means for comminuting the metal. For example, the container 8 and liquid 9 could be eliminated if a sufiicient distance is provided for the atomized particles to fall whereby the particles 12 are cooled sufiiciently in air to prevent sticking together.

The solidified particles 12 are then consolidated by working into an article, said working being of sufficient amount such that the densities of the article and of the solidified particles will be substantially the same. The resulting article may then be further worked by conventional methods and means into the desired shape or form.

Some of the alloy powders illustrated in Table I were treated by the successive steps of (a) cold compacting, (b) hot compacting, and (c) extrusion. The cold compacting was accomplished by placing the powder in a .638 ID. hardened steel die and successively pressing this charge from each end under a 25,000 p.s.i. pressure. Prior to charging the powder to the die, the rams and die walls were lubricated with a thin film of stearic acid and aluminum flake pigment in carbon tetrachloride. Upon completion of the cold compacting operation, the green billet was ejected from the die. The hot pressing of the green compacts was effected by replacing the normal extrusion die in the extrusion apparatus with a blank plug. The green compact was then placed in the heated chamber and subjected to a light load for approximately three minutes until the compact had reached the desired extrusion temperature. Pressure was then gradually applied until a load of 80,000 pounds per square inch was reached. This load was maintained for five minutes be fore being released. Upon completion of the hot pressing operation, the blank plug was removed and replaced with the desired extrusion die. After the extrusion die had reached temperature, the hot compacted billet was extruded at a rate of approximately 1.5 feet per minute. The extruded samples were subsequently straightened by means of a straight pull through a wire drawing die, the wire drawing die being sufficiently smaller than the extrusion to effect a small reduction in area.

The remaining alloys of Table 1 employed an alternative fabrication procedure which provided a more rapid fabrication technique whereby the cold compacting step prior to hot compacting was eliminated. This procedure consisted of charging the powder to a hot extrusion apparatus having a blank plug in place of the extrusion die, placing the ram immediately on top of the cold charge and subjecting the powder charge to a load of about 20,000 p.s.i. while the powder is heated up in the extrusion chamber. After the powder had reached the extrusion chamber temperature, the load was increased to approximately 100,000 p.s.i. to effect consolidation. The blank plug was then removed, replaced with the desired extrusion die and the consolidated material extruded as described above in connection with the first procedure.

Nonheat treated extrusions of all the alloys of Table I were tensile tested at 600 F. after being exposed to this temperature for 48 hours. The results of these tests are given hereinbelow in Table II. It will be noted that three subheadings, 13D, 8D and 4D appear under percent elongation. These subheadings indicate the gauge length for measuring the elongation in terms of the diameter of the specimen. For example, 13D means that the gauge length prior to testing was thirteen times the diameter of the specimen. The elongation is then expressed as a percentage of this length.

IABLE II- Entru- Percent Elonga Percent Alloy sion TS YS' tion Reduc- N o. Tempera- (p.s.i.) (p.s.i.) tion In ture, F. Area 13D 8D 4D Non-heat treated extrusions of all alloys of Table I were also tested at room temperature after being exposed to a temperature of 600 F. for 48 hours. Theresults of these tests are given in Table III below and the high properties obtaineddemons'trate the elevated temperature stability of these alloys.

TABLE III Room temperature properties of extrusions of powders [Extrusions were exposed to 600 F. for 48 hours prior to tensile testing] Extru- Percent Elonga- Percent Alloy sion TS YS tion Reduc- No. Tempera- (p.s.i.) (p.s.i.) tion In ture, F. Area 13D 8D 4D For purposes of comparison the properties of two conventional Wrought aluminum alloys, c.g. 7075-16 (nominal composition, 1.6% copper, 2.5% magnesium, 5.7% zinc, 0.25% chromium, balance aluminum) and 2014-T6 (nominal composition, 4.5% copper, 0.9% silicon, 0.8% manganese, 0.5 magnesium, balance aluminum) are given in Table IV below when measured at 600 F. and when. measured at roomte nperatureafter exposure to a temperature of 600 F. for the designated period of time.

TABLE IV Properties of conventional wrought alloys after exposure t0 600 F.

Measured at 600 F. Measured Time at at Room Alloy 600 F Temp,

Hrs TS Ys Elong. Ys

(p.s.i.) (ID-5,1.) (4D) (p.s.i.)

7075-T6 1/2 19, 500 7, 000 I 55 100 3,500 6,500 16,000 1/2- 10,000 9,000 30 s, 000 6, 500 50 14, 500

As be seen by comparison of the results shown in Table II, with Table IV, the improvements obtained in the 600 F. tensile properties by the additions of alloying ingredients in amounts exceeding that heretofore possible in the production of sound and workable cast bodies are very significant. From the results obtained with these alloys it can be seen that the new alloys containing such large amounts of alloying additions produced by the method of this invention have significantly higher tensile strengths and yield strengths at 600 F. than prior art aluminum base alloys produced by conventional methods, typical examples of which are given in Table IV.

Table II illustrates a large number of alloys exhibiting properties measured at 600 F. significantly superior to prior art alloys, the lowest properties being a tensile strength of 11,800 p.s.i. and a yield strength of 7,500 p.s.i. Tensile strengths as high as 27,600 p.s.i. and yield strengths as high as 19,500 p.s.i. were exhibited by alloysrcontaining the large amounts of alloying additions illustrated in Tables I and II produced by the method of this invention. In addition, from Table II it can be seen that more than two-thirds the alloys produced exhibited tensile strengths measured at 600 F. in excess of 15,000 p.s.i. and yield strengths measured at 600 F. in excess of 10,000 p.s.i.

In general, from reference to Table II, it may be seen that the various alloys set forth fall into the following groups with the recited mechanical properties when tested at 600 F. after exposure to 600 F. for 48 hours.

(1) Alloys consisting essentially of 3 to 10% manganese, balance aluminum and impurities in normal amounts having a tensile strength from about 15,000 to about 18,000 p.s.i., a yield strength from about 8,000 to 12,000 p.s.i., and an elongation from about 16 to 25% in a length 13 timcsthe diameter of a cylindrical test specimen.

(2) Alloys consisting essentially of 1 to 6% zirconium, balance aluminum and impurities in normal amounts having a tensile strength from about 13,000 to 14,000 p.s.i., a yield strength from about 8,000 to 9,000 p.s.i., and an elongation from about 19 to 23% in a length 13 times the diameter of a cylindrical test specimen.

(3) Alloys consisting essentially of 3 to 12% iron, balance aluminum and impurities in normal amounts having a tensile strength from about 18,000 to 23,000 p.s.i., a yield strength from about 14,000 to 18,000 p.s.i. and an elongation from about 6 to 14% in a length 13 times the diameter of a cylindrical test specimen.

(4) Alloys consisting essentially of 2.5 to 5% molybdenum, balance aluminum and impurities in normal amounts having a tensile strength from about 11,000 to 14,000 p.s.i., a yield strength from about 8,000 to 11,000 p.s.i., and an elongation from about 11 to 12% in a length 13 times the diameter of a cylindrical test specimen.

(5) .Alloys consistingessentially of 1 to 6% .chro' mium, balance aluminum and irnnu 'ties in marina) amounts, having a tensile strength from about 12,000 to 18,000 p.s.i., a yield strength from about 9,000 to 13.000 p.s.i., and an elongation of about 11% in a length 13 times the diameter of a cylindrical test specimen.

(6) Alloys consisting essentially of 0.5 to 4% titanium, balance aluminum and impurities in normal amounts having a tensile strength from about 14,000 to 16,000 p.s.i., a yield strength from about 11,000 to 13,000 p.s.i., and an elongation from about 18 to 20% in a length 13 times the diameter of a cylindrical test specimen.

(7) Alloys consisting essentially of 0.1 to 2.5% vanadium, balance aluminum and impurities in normal amounts having a tensile strength from about 11,000 to 13,000 p.s.i., a yield strength from about 7,000 to 8,000 p.s.i., and an elongation of about 18% in a length 13 times the diameter of a cylindrical test specimen.

(8) Alloys consisting essentially of 4.5 to 13% copper, 1.5 to 5% manganese, 0.2 to 2% zirconium, 0.1 to 1% vanadium, balance aluminum and impurities in normal amounts having a tensile strength from about 17,000 to 19,000 p.s.i., a yield strength from about 12,000 to 15,000 p.s.i., and an elongation from about 12 to 28% in a length 13 times the diameter of a cylindrical test specimen.

(9) Alloys consisting essentially of 7.5% iron, an element chosen from the group of 2% chromium, 2% titanium and 2% zirconium, balance aluminum and impurities in normal amounts having a tensile strength from about 23,000 to 28,000 p.s.i., a yield strength from about 16,000 to 20,000 p.s.i., and an elongation from about 10 to 15% in a length 13 times the diameter of a cylindrical test specimen.

(l) Alloys consisting essentially of 3.5 to manganese, one or more of the elements chosen from the group 2 to 7.5% iron, 1% chromium, 0.5 to 2% titanium, 1 to 2% zirconium and 0.5 to 1% vanadium, balance aluminum and impurities in normal amounts having a tensile strength from about 13,000 to 25,000 p.s.i., a yield strength from about 8,000 to 18,000 p.s.i. and an elongation from about 3 to 22% in a length 13 times the diameter of a cylindrical test specimen.

The room temperature tensile properties of the extrusions of alloys produced in accordance with this invention after exposure to 600 F. can be seen by comparison of Table III with Table IV to be superior to those found in conventional wrought aluminum alloys after a similar exposure to 600 F. Several of these compositions were outstanding in this respect and exhibited tensile strengths in excess of 60,000 p.s.i. and yield strengths in excess of 50,000 p.s.i. The lowest yield strength shown in Table III is 19,700 p.s.i., which is substantially higher than that exhibited by alloy 7075-T6 of Table IV.

It was also found in accordance with the present invention that the alloys exhibited substantially high modulus of elasticity values. For example, alloys 9, 12 and 15 as designated in Table I had the following values for modulus of elasticity:

P.s.i. Alloy No. 9 12.5)(10 Alloy No. 12 11.s 10 Alloy No. 15 10.8)(10 form coarse primary crystals of intermediate phases with aluminum or other alloying additions and cause severe chemical segregation during solidification, heating said melt to a temperature at which it is a homogeneous liquid solution, comminuting said homogeneous liquid solution, solidifying and cooling the resulting metal particles at a rate sufficiently rapid to eliminate or substantially eliminate the formation of coarse crystals of intermediate phases and consolidating the solidified particles by working.

2. A method according to claim 1 wherein said comminuting step is effected by atomizing the homogeneous liquid solution.

3. A method of producing an aluminum base alloy article characterized by superior elevated temperature properties comprising the steps of preparing a melt of an aluminum base alloy containing alloying additions of metals in amounts which under conditions of production heretofore known would form coarse primary crystals of intermediate phases with aluminum or. other alloying additions and cause severe chemical segregation during solidification, heating said melt to a temperature at which it is a homogeneous liquid solution, comminuting said liquid solution, solidifying and cooling the resulting metal particles sufiiciently rapid to eliminate or substantially eliminate the formation of coarse crystals of intermediate phases, consolidating the solidified particles into an article by working, said working being of sufficient amount that the densities of the article and solidified particles are sub? stantially the same.

4. A method according to claim 3 wherein said comminuting step is effected by atomizing the homogeneous liquid solution.

5. A method of producing an aluminum base alloy article characterized by superior elevated temperature properties comprising the steps of preparing a melt of an aluminum base alloy containing alloying additions of at least one of the elements chromium, manganese, iron, zirconium, titanium, vanadium and molybdenum in amounts exceeding that heretofore possible in the production of sound and workable cast bodies, heating said melt to a temperature at which it is a homogeneous liquid solution, comminuting said liquid solution, solidifying and cooling the metal particles at a rate sufiiciently rapid to prevent the formation of coarse crystals of intermediate phases and consolidating said particles into an article by working, said working being of suflicient amount that the densities of the article and of the solidified particles are substantially the same.

6. A method according to claim 5 wherein the comminuting step is effected by atomizing the homogeneous liquid solution.

7. A method of producing an aluminum base alloy article characterized by superior elevated temperature properties, comprising the steps of heating a melt of an aluminum base alloy containing alloying additions in amounts exceeding that heretofore possible in the production of sound and workable cast bodies to a temperature at which it is a homogeneous liquid solution, comminuting said liquid solution, rapidly cooling and solidifying the metal particles, cold compacting followed by hot compacting of said comminuted particles, and further working the compacted material.

8. A method of producing an aluminum base alloy article, characterized by superior elevated temperature properties comprising the steps of heating a melt of an aluminum base alloy containing alloying additions of metals in amounts which under conditions of production heretofore known would form coarse primary crystals of intermediate phases with aluminum or other alloying additions and would cause severe chemical segregation during solidification to a temperature at which it is a homogeneous liquid solution, comminuting said liquid solution, rapidly solidifying and cooling the metal particles, cold 'compacting followed'by hot comp c i of said solidified particles, and subjecting the compacted material to further working.

9. A method of producing an aluminum base alloy article, characterized by superior elevated temperature properties comprising the steps of heating a melt of an aluminum base alloy containing alloying additions of at least one of the elements, chromium, manganese, iron, zirconium, titanium, vanadium and molybdenum, in amounts exceeding that heretofore possible in the production of sound and workable cast bodies to a temperature at which it is a homogeneous liquid solution, comminuting said liquid solution, solidifying and cooling the metal particles at a rate sufliciently rapid to eliminate or substantially eliminate the formation of coarse crystals of intermediate phases, cold compacting followed by hot compacting of said comminuted particles, and subjecting the compacted material to further working.

10. A method of producing an aluminum base alloy article characterized by superior elevated temperature properties comprising the steps of preparing a melt of an aluminum base alloy containing alloying additions in amounts exceeding that heretofore possible in the production of sound and workable cast bodies, heating said melt to a temperature at which it is a homogeneous liquid solution, comminuting said liquid solution, solidifying and cooling the resulting metal particles sufficiently rapid to eliminate or substantially eliminate the formation of coarse crystals of intermediate phases, hot compacting the solidified particles and subjecting the compacted material to further working.

11. A method of producing an aluminum base alloy article characterized by superior elevated temperature properties comprising the steps of preparing a melt of an aluminum base alloy containing alloying additions of metals in amounts which under conditions of production heretofore known would form coarse primary crystals of intermediate phases with aluminum or other alloying additions and would cause severe chemical segregation during solidification, heating said melt to a temperature at which it is a homogeneous liquid solution, comminuting said liquid solution, solidifying and cooling the resulting metal particles sufficiently rapid to substantially eliminate the formation of coarse crystals of intermediate phases, hot compacting said solidified particles, and subjecting the compacted material to further working.

12. A method of producing an aluminum base alloy article characterized by superior elevated temperature properties comprising the steps of preparing a melt of an aluminum base alloy containing alloying additions of at least one of the elements chromium, manganese, iron, zirconium, titanium, vanadium and molybdenum in amounts exceeding that heretofore possible in the production of sound and workable cast bodies, heating said melt to a temperature at which it is a homogeneous liquid solution, comminuting said liquid solution, solidifying and cooling the metal particles at a rate sufliciently rapid to substantially eliminate the formation of coarse crystals of intermediate phases, hot compacting said solidified particles and subjecting the compacted material to further working.

13. A method of producing an aluminum base alloy article, characterized by superior elevated temperature properties comprising the steps of heating a melt of an aluminum base alloy containing alloying additions of at 10 least one of the elements, chromium, manganese, iron, zirconium, titanium, vanadium and molybdenum in amounts exceeding that heretofore possible in the production of sound and workable cast bodies to a temperature at which it is a homogeneous liquid solution, pouring the molten metal into a container having a tubular passage at the bottom thereof whereby said molten metal passes through said tubular passage, directing at least one jet of gas into the molten metal passing from said tubular passage thereby atomizing said molten metal, solidifying and cooling the metal particles sufficiently rapid to eliminate or substantially eliminate the formation of coarse crystals of intermediate phases, said metal particles dropping into a cool liquid where they are collected, compacting said particles at an intermediate pressure while heating to the extrusion temperature, increasing the compacting pressure to a maximum upon reaching extrusion temperature, and extruding the compacted material.

14. The method of claim 13 wherein said intermediate pressure is approximately 20,000 p.s.i. and said maximum compacting pressure is approximately 100,000 p.s.i.

15. A method of producing an aluminum base alloy article, characterized by superior elevated temperature properties comprising the steps of heating a melt of an aluminum base alloy containing alloying additions of at least one of the elements, chromium, manganese, iron, zirconium, titanium, vanadium, and molybdenum in amounts exceeding that heretofore possible in the production of sound and workable cast bodies to a temperature at which it is a homogeneous liquid solution, pouring the molten metal into a container having a tubular passage at the bottom thereof whereby said molten metal passes through said tubular passage, directing at least one jet of gas into the molten metal passing from said tubular passage thereby atomizing said molten metal, solidifying and cooling the metal particles at a rate sufficiently rapid to eliminate or substantially eliminate the formation of coarse crystals of intermediate phases, said metal particles dropping into a cool liquid where they are collected, cold compacting said particles at an intermediate pressure, further compacting said particles at a low pressure while heating to the extrusion temperature, increasing the compacting pressure to a maximum upon reaching the extrusion temperature, and extruding the compacted material.

16. The method of claim 15 wherein said cold compacting pressure is approximately 25,000 p.s.i. and said maximum compacting pressure is approximately 100,000 p.s.i.

References Cited in the file of this patent UNITED STATES PATENTS 1,659,291 Hall Feb. 14, 1928 2,369,354 Kempf et al. Feb. 13, 1945 2,589,175 Weinrich Mar. 11, 1952 2,630,623 Chisholm et al Mar. 10, 1953 2,657,796 Leontis et al Nov. 3, 1953 2,679,932 Burns June 1, 1954 FOREIGN PATENTS 638.581 Great Britain June 14. 1950 532,700 Canada Nov. 6, 1956 

1. A METHOD OF PRODUCING METAL ARTICLES COMPRISING THE STEPS OF PREPARING A MELT OF AN ALUMINUM BASE ALLOY CONTAINING ALLOYING ADDITIONS OF METALS IN AMOUNTS WHICH UNDER CONDITIONS OF PRODUCTION HERETOFORE KNOWN WOULD FORM COARSE PRIMARY CRYSTALS OF INTERMEDIATE PHASES WITH ALUMINUM OR OTHER ALLOYING ADDITIONS AND CAUSE SEVERE CHEMICAL SEGREGATION DURING SOLIDIFICATION, HEATING SAID MELT TO A TEMPERATURE AT WHICH IT IS A HOMOGENEOUS LIQUID SOLUTION, COMMINUTING SAID HOMOGENEOUS LIQUID 